Can I join shelves from two separate stack into one stack

Hello,

We have FAS8060 running 8.3.2 CDOT.  We have two stacks , Stack A have 5 shelves 30-34, Stack B has one shelf 40. They are exactly the same shelf model and speed and the disks are also the same. I want to combine them to free up the SAS port. Im guessing this will require downtime? I am thinking, re-id shelf 40 to shelf 35 then add to Stack A. I just need to know if downtime is required.

Thanks.